Atlantic Ocean

Despite the large size of this region, only 155 eruptions are known–only Antarctica has less–but its historical record is relatively long. The largest island group, the Canaries, is reached by favorable winds from Europe and was an important base for early voyages to the new world. In fact, Christopher Columbus recorded a 1492 eruption on Tenerife, just 7 weeks before that same logbook carried documentation of a more historic observation. The Azores were also well placed for sailors because of the predominant westerly winds used for return routes to Europe.
The Canaries were mentioned by Pliny around 40 AD, and were often rediscovered in the following centuries. They were claimed by Portugal in 1341, the year of the region's first historical eruption (a somewhat questionable report of activity somewhere on Tenerife), but were awarded to Spain by the Pope 3 years later. They were settled in 1402 and conquest of the indigenous Guanches population was complete by 1496. The Canaries now have the largest population (1.6 million) in the region and, as part of Spain, claim Pico de Teide as that nation's highest point.
A discovery date for the Azores is uncertain, but they appear on a map from 1351 AD. The Portuguese visited in 1427-31 and colonization began in 1445, a year after the first historical eruption. The 9 islands now support about 250,000 people, half of them on the island of Sao Miguel.

The Cape Verde islands were discovered by Portugal in 1456 and settled 6 years later. An eruption beginning in 1500 appears to have continued for about 260 years, with behavior similar to that of Italy's Stromboli. The islands were an important point in the trans-shipment of slaves until the 18th century. Independence from Portugal came in 1975.
Tristan da Cunha was discovered by the Portuguese in 1506 and the islands were much visited by whalers and sealers. They were first inhabited by St. Helenans in the 19th century and annexed by Britain in 1816. An eruption in 1961 broke out at the only inhabited area on the island, forcing residents to evacuate, but most elected to return within two years and the 1970 population was estimated at 280. In 2004 submarine eruptive activity was recorded near Nightingale Island at the southern end of the Tristan da Cunha island group. No previous Holocene activity was known from Nightingale Island, but an earthquake swarm lasting 6 hours beginning on July 29, 2004 was followed by observation of large blocks of floating phonolitic pumice that washed up on Tristan da Cunha. The event was considered to have originated from an eruption associated with an earthquake swarm 37-53 km SSE of Tristan da Cunha on the submarine SE flank of Nightingale Island. Aside from other submarine activity (most of it uncertain) the only other dated eruption in the South Atlantic region is from Norway's Bouvet Island, the most remote in the world. It was discovered in 1739, but it's only known eruption was 2000 years ago (by magnetic dating).

Volcanism in the region is largely caused by hotspots in oceanic crust, and the region has the highest proportion of fissure vent volcanoes (as primary features). Several known volcanoes lie along or near the Mid-Atlantic Ridge that separates the Eurasian and African plates from the North and South American plates, but the Canaries and Cape Verdes lie just west of the African continental margin. This region has been relatively quiet, with only 14 eruptions confirmed since 1900, including the two mentioned above in the Tristan da Cunha island group. No eruptions have occurred in the Canaries following small eruptions on La Palma in 1949 and 1971. The only confirmed eruption in the Azores since a 1907 submarine eruption at Monaco Bank took place along a fissure west of Terceira Island in 1998, when floating and steaming lava blocks were observed. Fogo volcano in the Cape Verde Islands erupted in 1951, but was quiet until 1995, when a new cinder cone produced lava flows that buried a village and croplands on the caldera floor.